Osteoid Osteoma The osteoid osteoma is the most common osteoid-forming tumorseen in the skeletal system, accounting for 10% of all benignbone tumors. It is more common in males than females with thepeak incidence in the second decade of life. The lesions producesymptoms of dull, aching pain that is more severe at night. Thepain is relieved with anti-inflammatory medication such asaspirin or non-steroidal anti-inflammatory drugs (NSAID)that inhibit the high concentration of prostaglandins found inthe nidus of the osteoid osteoma. The lesions occur typically inthe cortical structures of long bones such as the femur or tibiabut can also be found in the small bones of the ankle, wrist orvertebral column. The lesion is characteristic for its dense,sclerotic response in the cortical bone resulting in a fusiformenlargement on the surface of the cortex as a response to thesmall inflammatory nidus or granuloma (measuring up to one
centimeter in diameter) in the central area of the scleroticresponse. If the lesion is located in a central medullary area,such as the metaphysis or on the very superficial surface of abone, the sclerotic response is less severe. If the nidus islocated close to or within a joint structure, as in the femoralneck area, there will be a significant inflammatory synovitisin the adjacent joint that gives the clinical appearance of apyarthrosis. In the spine, the lesions are usually located in theposterior elements of the spine such as the laminae or pedicles.The lumbar spine is the most common location followed secondby the dorsal spine. Atypical secondary painful scoliosis willdevelop with the convexity seen on the side opposite theinflammatory lesion. The two most significant diagnostic imaging studies are a CTscan through the nidus area to identify its anatomic location and abone isotope scan which is invariably positive, especially in asymptomatic lesion. It is the current feeling that the osteoid.
osteoma is a true benign neoplasm of bone in which a com-bination of osteoclastic and osteoblastic activity are seen.There are no inflammatory cells such as lymphocytes orplasma cells as would be seen in a Brodie’s abscess. Non-steroidal anti-inflammatory medications such as prostaglandininhibitors can be very effective in controlling the disablingsymptoms and helping the patient get thru a period of one ortwo years during which time the lesion will typically involuteinto a painless lesion that does not require surgery. However,if the patient is unable to live with the pain during this time,a surgical approach is indicated. Following exposure of thelesion, a high speed burr is used to burr into the inflammatorybone that is characterized by a pinkish hyperemia. When thenidus is found, a small curette is used to core the inflammatorynidus for pathological diagnosis and the cavity of the nidusis burred an additional 2 or 3 mm which usually results in a verydramatic relief of symptoms and a permanent cure from the
disease process. It is not necessary to remove the largedense sclerotic bone surrounding the nidus; doing so couldresult in a pathologic fracture following surgery. In the spine,a simple laminectomy is frequently carried out. If the lesion islocated in the pedicle a simple burring into the pedicle willrelieve the patient of the inflammatory pain. More recently, relatively non-invasive techniques have beentried to remove the nidus of the osteoid osteoma by means of aCT guided burr placed through a protective trocar or by place-ment of a heat-producing radio frequency probe that, whenproperly positioned, can destroy the nidus through thermalcoagulation. These techniques are particularly valuable for deep-seated lesions located in the acetabulum. For lesions located inthe pedicle of a vertebra one must be careful not to damage anadjacent spinal root or spinal cord.
CLASSICCase #119 yr old female painfulOsteoid osteoma nidusfemur
Osteoblastoma The so-called osteoblastoma is considered by most to be a largeor giant form of the similar clinical entity known as the osteoidosteoma. As with the osteoid osteoma, it is found in children andyoung adults, more often in males than females. It is less commonthan the osteoid osteoma, representing approximately 1% of allbone tumors. It is found mostly in metaphyseal areas of long boneand in the posterolateral elements of the axial skeleton wherenearly 50% of the lesions are identified. Radiographically theselesions are more osteolytic than the osteoid osteoma and have acentral nidus that measures more than 1.5 cm in diameter withless reactive sclerosis seen at the periphery than an osteoidosteoma. It is not unusual for an aneurysmal component to beassociated with the osteoblastoma, similar to the reaction seenadjacent to chondroblastomas and giant cell tumors. The micro-scopic appearance of the nidus material is almost identical to
that of the osteoid osteoma and under higher power cannot bedifferentiated by even the most competent pathologists. Themajor concern is a microscopic appearance similar to an osteo-sarcoma and, for this reason, multiple samples must be evaluatedin order to establish the correct diagnosis in cases where theselesions arise from the metaphyseal areas of long bone. In the spinal area, the osteoblastoma is typically located in theposterolateral elements where it can cause problems with spinalcord or nerve root compression that may require aggressivesurgical decompression and even spinal stabilization. On occasionan osteoblastoma will spontaneously convert into an osteo-sacoma, especially if it has been treated with radiation therapy.The primary treatment for the osteoblastoma is a surgical one witha fairly aggressive curettement of the lesion. There is no particularreason to take wide margins because the recurrence rate is quitelow and in some cases the lesions resolve spontaneously with outany surgery at all, similar to what occurs with osteoid osteomas.
A variant of the osteoblastoma, the so-called aggressive or“malignant” osteoblastoma, is a clinical entity halfway between theclassic benign osteoblastoma and a full blown malignant osteo-sarcoma. This “malignant” osteoblastoma appears and behavesclinically at the local site like an osteosarcoma but has no potentialto metastasize to distant parts. In this situation, local treatmentmust be more aggressive and probably would require a wide localresection to avoid a local recurrence because radiation therapy oreven systemic chemotherapy is not effective for this aggressive butbenign entity.
Osteofibrous Dysplasia Osteofibrous dysplasia is a rare condition occurringin children less than 10 years of age. This benign lesionhas radiographic and microscopic features similar to fibrousdysplasia of the tibia, the main difference being the presenceof more heavily ossified tissue at the periphery of the lesiongiving it a soap-bubbly appearance on x-ray. Microscopicallyit has a similar “alphabet-soup” metablastic bone appearancein a benign fibrous tissue stroma but with the additional featureof heavy osteoblastic rimming of the trabeculae not seen infibrous dysplasia. It typically arises from the anterior cortex ofthe tibia at mid shaft and causes a progressive anterior bowingof the tibia over time, creating a cosmetic deformity associatedwith pain of a dull, aching nature. The radiographic appearanceIs very similar to and impossible to separate from that of theMalignant adamantinoma that also affects the tibia in children
and, for this reason, a biopsy must be performed to rule out themalignant possibility. Occasionally osteofibrous dysplasia of thetibia can progress gradually into a well-differentiated formof the adamantinoma, which will have the microscopicfeatures of both osteofibrous dysplasia and adamantinomain the same lesion. As far as treatment is concerned, earlysurgical debriedment and bone grafting before age 15 yearsresults in a high local recurrence rate and thus should bediscouraged until the child reaches full bone maturity at whichtime a definitive debriedment and bone grafting procedurecan be performed without significant risk of recurrence. Thislesion occurs bilaterally in a very small percentage of casesand can also involve the fibula on the same side. This processin newborns appears to be more osteolytic and destructive innature.
CLASSICCase #95 9 yr male osteofibrous dysplasia tibia
Ossifying Fibroma of Jawbone Ossifying fibroma of jawbone is a benign condition similar toosteofibrous dysplasia of the tibia in that histologically they arealmost identical. It is also a condition that is related to fibrousdysplasia, which can have a very similar radiographic appearance,but in the case of fibrous dysplasia of jawbone osteoblasticrimming of the trabecular bone is not seen under microscopicevaluation. As with fibrous dysplasia, this condition is found inchildren and is almost always an asymptomatic process resultingin cosmetic deformation of the maxilla or mandible, usually onone side but can be bilateral. The condition can result insignificant malocclusion of the teeth because of deformationof the subadjacent alveolar ridge or maxillary structures. It alsocan create problems with normal drainage from the air sinuses inthe maxilla that can lead to infection requiring surgical drainage.Most of the surgical treatment for this condition is for cosmeticdeformity.
Case #102 5 yr female ossifying fibroma maxilla